Aqueous polysiloxane emulsions with mica treated with organosilicon compound

Abstract

Aqueous diorganopolysiloxane emulsions containing dispersed inorganic silicates which have been treated with an organosilicon compound to impart hydrophobic properties thereto. The resultant dispersions may be employed as release agents especially in molding tires.

What is claimed is: 
     
       1. An aqueous emulsion containing a diorganopolysiloxane having a viscosity of at least 1000 cP at 25° C. and having mica dispersed therein which has a particle size of from 0.02 to 0.25 mm, said mica having been treated with an organosilicon compound selected from the class consisting of octamethylcyclotetrasiloxane, hydroxyl-terminated dimethylpolysiloxanes having from 2 to 12 siloxane units per molecule and silicon compounds having the formula   (R.sub.3 Si).sub.a Z and R.sub.a' SiZ'.sub.4-a'     in which R is selected from the class consisting of monovalent hydrocarbon radicals having from 1 to 18 carbon atoms and halogenated hydrocarbon radicals, Z and Z' are radicals selected from the class consisting of halogen, hydrogen, --OH, --OR', --NR'X, --ONR', --SR', --OOCR' and when a is 2, then Z is also selected from the class consisting of --O--, ═NX and --S--, R' is selected from the class consisting of a hydrocarbon radical and a substituted hydrocarbon radical, X is selected from the class consisting of hydrogen and R', a is 1 or 2 and a' is 1, 2 or 3.   
     
     
       2. The aqueous diorganopolysiloxane emulsion of claim 1, wherein the mica has been treated with an organosilane having the general formula:   R.sub.a'.sup.1 SiOR.sub.4-a'.sup.2     in which R 1  is a hydrocarbon radical having from 1 to 18 carbon atoms, R 2  is selected from the class consisting of alkyl radicals having from 1 to 4 carbon atoms and methoxyethylene radicals and a' is 1, 2 or 3.   
     
     
       3. The aqueous diorganopolysiloxane emulsion of claim 1, wherein the mica has been treated with an organosilicon compound at the rate of 0.1 to 10 percent by weight, based on the weight of the mica. 
     
     
       4. An aqueous dispersion containing: 2 to 25 percent by weight of a diorganopolysiloxane having a viscosity of at least 1000 cP at 25° C.   20 to 60 percent by weight of mica having a particle size of from 0.02 to 0.25 mm which has been treated with an organosilicon compound selected from the class consisting of octamethylcyclotetrasiloxane, hydroxyl-terminated dimethylpolysiloxanes having from 2 to 12 siloxane units per molecule and silicon compounds having the formula   (R.sub.3 Si).sub.a Z and R.sub.a', SiZ'.sub.4-a'        in which R is selected from the class consisting of monovalent hydrocarbon radicals having from 1 to 18 carbon atoms and halogenated hydrocarbon radicals, Z and Z' are radicals selected from the class consisting of halogen, hydrogen, --OH, --OR', --NR'X, --ONR', --SR', --OOCR' and when a is 2, then Z is also selected from the class consisting of --O--, ═NX and and --S--, R' is selected from the class consisting of a hydrocarbon radical and a substituted hydrocarbon radical, X is selected from the class consisting of hydrogen and R', a is 1 or 2 and a' is 1, 2 or 3,   0.10 to 5.0 percent by weight of a dispersing agent   0 to 25 percent by weight of lubricants other than the mica and diorganopolysiloxane   0.01 to 1.5 percent by weight of a thickening agent   0.01 to 1.0 percent by weight of a bactericide and at least   20 percent by weight of water,   in which the percent by weight is based on the total weight of the dispersion.